Bulat is a type of steel alloy known in Russia from medieval times and regularly mentioned in Russian legends as material of choice for cold steel. The name bulat is a Russian transliteration of the Persian word پولاد (transliterated pulad), meaning steel. There are no known sources indicating that the origin of bulat is Russian while the name suggests that the immediate source of it was Persia. It is highly possible that bulat steel is made using the same process as wootz steel.
The secret of bulat manufacturing was lost by the beginning of the 19th century. Pavel Petrovich Anosov eventually managed to duplicate the qualities of that metal in 1838, when he completed ten years of study into the nature of Damascus steel swords. Bulat became popular in cannon manufacturing, until the Bessemer process was able to make the same quality steels for far less money.
Anosov had entered the Saint Petersburg Mine Cadet School in 1810, where a Damascus steel sword was stored in a display case. He became enchanted with the sword, and was filled with stories of them slashing through their European counterparts. In November 1817 he was sent to the factories of Zlatoust mining region in the southern Urals, where he was soon promoted to the inspector of the "weapon decoration department".
Here he again came into contact with Damascus steel of European origin (which was in fact pattern welded steel, and not at all similar), but quickly found that this steel was quite inferior to the original from the Middle East. Anosov had been working with various quenching techniques, and decided to attempt to duplicate Damascus steel with quenching. He eventually developed a methodology that greatly increased the hardness of his steels.
Carbon steel consists of two components: pure iron, in the form of ferrite, and cementite or iron carbide, a compound of iron and carbon. Cementite is very hard and brittle; its hardness is about 640 by the Brinell hardness test, whereas ferrite is only 200. The amount of the carbon and the cooling regime determine the crystalline and chemical composition of the final steel. In bulat, the slow cooling process allowed the cementite to precipitate as micro particles in between ferrite crystals and arrange in random patterns. The color of the carbide is dark while steel is grey. This mixture is what leads to the famous patterning of Damascus steel.
Since cementite is essentially a ceramic, this also accounts for the famous sharpness of the Damascus (and bulat) steel. Cementite is unstable and breaks down between 600-1100°C into ferrite and carbon, so working the hot metal must be done very carefully.
• The Mystery of Damascus Blades, by John D. Verhoeven in Scientific American, No 1, pages 74-79, 2001.
• History of Metallography: The Development of Ideas on the Structure of Metals before 1890. Cyril S. Smith. MIT Press, 1988.
• On Damascus Steel. Leo S. Figiel. Atlantis Arts Press, 1991.
• Archaeotechnology: The Key Role of Impurities in Ancient Damascus Steel Blades. J. D. Verhoeven, A. H. Pendray and W. E. Dauksch in
• JOM: A Publication of the Minerals, Metals and Materials Society, Vol. 50, No. 9, pages 58–64; September 1998. Available at http://www.tms.org/pubs/journals/JOM/9809/Verhoeven-9809.html
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Mokume-gane ( 木目金 ) is a mixed-metal laminate with distinctive layered patterns. Translating as "wood-grain metal", the name was borrowed from one type of pattern created in the forging of swords and other edged weapons.
First made in 17th-century Japan, the mixed-metal was used only for sword fittings until the Meiji era, when the decline of the katana industry forced artisans to create purely decorative items instead. The inventor, Denbei Shoami (1651-1728), initially called his product "guri bori" for its simplest form's resemblance to "guri", a type of carved lacquerwork with alternating layers of red and black. Other historical names for it were kasumi-uchi (cloud metal), itame-gane (wood-grain metal), and yosefuki. (Pijanowski & Pijanowski, 2001)
The traditional components were relatively soft metallic elements and alloys - gold, copper, silver, shakudo, shibuichi, and kuromido - which would form liquid phase diffusion bonds with one another without completely melting. After the original metal sheets were stacked and carefully heated, the solid billet of simple stripes could be forged and carved to increase the pattern's complexity. To achieve a successful lamination using the traditional process required a highly skilled smith with a great deal of experience.
The modernized process typically uses a controlled atmosphere in a temperature controlled furnace. Mechanical aids such as a hydraulic press or torque plates (bolted clamps) are also typically used to apply compressive force on the billet during lamination and provide for the implementation of lower temperature solid-state diffusion between the interleaved layers, allowing the inclusion of many nontraditional components such as titanium, platinum, iron, bronze, brass, nickel silver, and various colors of karat gold including yellow, white, sage, and rose hues as well as sterling silver. (Binnion & Chaix, 2002)
To increase the contrast between the laminate layers many mokume-gane items are colored by the application of a patina (a controlled corrosion layer) to accentuate or even totally change the colors of the metal's surface. One example of a traditional Japanese patination is the use of rokusho. Rokusho is a complex copper verdigris compound produced specifically for use as a patina.
To color the shakudo and gold, submerse the piece in boiling rokusho, and hold there - agitating constantly - until it reaches the desired color. Rokusho colors shakudo a black-purple. The more gold is in the alloy, the more purple it turns.
Rokusho is produced in small batches in a traditional process and is somewhat difficult to acquire outside Japan. There are some proposed substitute formulas (see rokusho article.)
Traditionally a paste of ground daikon radish is also used to prepare the work for the patina.
The paste is applied immediately before the piece is boiled in the rokusho to protect the surface against tarnish and uneven coloring.
(Pijanowski & Pijanowski, 2001)
Shakudo can also be darkened by adding salt with ammonia in a plastic bag. The warmer the solution, the faster it will darken the metal.
• Pijanowski, H.S. and Pijanowski, G.M. (2001). Wood Grained Metal: Mokume-Gane. http://www.silversmithing.com/1mokume.htm
. Retrieved on 2007-01-26.
• Binnion, J. E. and Chaix, B. (2002) (PDF). Old Process, New Technology: Modern Mokume Gane. http://www.mokume-gane.com/Papers/PaperThankyou.html
. Retrieved on 2007-01-26.
This entry is from Wikipedia, the leading user-contributed encyclopedia.